Two-dimensional (2D) ReSe2 has attracted considerable interest due to its unique anisotropic mechanical, optical, and exitonic characteristics. Recent transient absorption experiments demonstrated a prolonged lifetime of photoexcited charge carriers by stacking ReSe2 with MoS2, but the underlying mechanism remains elusive. Here, by combining time-domain density functional theory with nonadiabatic molecular dynamics, we investigate the electronic properties and charge carrier dynamics of 2D ReSe2/MoS2 van der Waals (vdW) heterostructure. ReSe2/MoS2 has a type II band alignment that exhibits spatially distinguished conduction and valence band edges, and a built-in electric field is formed due to interface charge transfer. Remarkably, in spite of the decreased band gap and increased decoherence time, we demonstrate that the photocarrier lifetime of ReSe2/MoS2 is ∼5 times longer than that of ReSe2, which originates from the greatly reduced nonadiabatic coupling that suppresses electron–hole recombination, perfectly explaining the experimental results. These findings not only provide physical insights into experiments but also shed light on future design and fabrication of functional optoelectronic devices based on 2D vdW heterostructures.

The BP/SnSe vdW heterostructure is a promising photovoltaic materials and the power conversion efficiency can reach to 17.24%.

Point defects in semiconductors usually act as nonradiative charge carrier recombination centers, which severely limit the performance of optoelectronic devices. In this work, by combining time-domain density functional theory with nonadiabatic molecular dynamics simulations, we demonstrate suppressed nonradiative charge carrier recombination and prolonged carrier lifetime in two-dimensional (2D) ReX 2 (X = S, Se) with S/Se vacancies. In particular, a S vacancy introduces a shallow hole trap state in ReS 2 , while a Se vacancy introduces both hole and electron trap states in ReSe 2 . Photoexcited electrons and holes can be rapidly captured by these defect states, while the release process is slow, which contributes to an elongated photocarrier lifetime. The suppressed charge carrier recombination lies in the vacancy-induced lowfrequency phonon modes that weaken electron−phonon coupling, as well as the reduced overlap between electron and hole wave functions that decreases nonadiabatic coupling. This work provides physical insights into the charge carrier dynamics of 2D ReX 2 , which may stimulate considerable interest in using defect engineering for future optoelectronic nanodevices.

Recent years have witnessed a surge of research in twodimensional (2D) ferroelectric structures that may circumvent the depolarization effect in conventional perovskite oxide films. Herein, by first-principles calculations, we predict that an orthorhombic phase of lead(II) oxide, PbO, serves as a promising candidate for 2D ferroelectrics with good stability. With a semiconducting nature, 2D ferroelectric PbO exhibits intrinsic valley polarization, which leads to robust ferroelectricity with an in-plane spontaneous polarization of 2.4 × 10 −10 C/m and a Curie temperature of 455 K. Remarkably, we reveal that the ferroelectricity is strain-tunable, and ferroelasticity coexists in the PbO film, implying the realization of 2D multiferroics. The underlying physical mechanism is generally applicable and can be extended to other oxide films such as ferroelectric SnO and GeO, thus paving an avenue for future design and fabrication of functional ultrathin devices that are compatible with Si-based technology.

The power of surface chemistry to create atomically precise nanoarchitectures offers intriguing opportunities to advance the field of quantum technology. Strategies for building artificial electronic lattices by individually positioning atoms or molecules result in precisely tailored structures but lack structural robustness. Here, taking the advantage of strong bonding of Br atoms on noble metal surfaces, we report the production of stable quantum corrals by dehalogenation of hexabromobenzene molecules on a preheated Au(111) surface. The byproducts, Br adatoms, are confined within a new surface reconstruction pattern and aggregate into nanopores with an average size of 3.7 ± 0.1 nm, which create atomic orbital-like quantum resonance states inside each corral due to the interference of scattered electron waves. Remarkably, the atomic orbitals can be hybridized into molecular-like orbitals with distinct bonding and antibonding states. Our study opens up an avenue to fabricate quantum structures with high yield and superior robustness.